Super-elastic, hydrophobic composite aerogels for triboelectric nanogenerators

Progress toward the advancement of environmentally friendly energy harvesting devices is critical for eco-environmental protection. There is an urgent need for developing energy harvesting devices from biobased materials. However, it is still a challenge to utilize biobased cellulose nanofiber (CNF) aerogels in triboelectric nanogenerators (TENGs) due to their poor mechanical properties, hydrophilicity, and weak polarization capability. Here, we demonstrate a facile strategy to fabricate a super-elastic, hydrophobic CNF/MXene composite aerogel for TENGs through fluorosilane crosslinking and a directional freeze-dried assembled structure. This aerogel can withstand up to 80% compressive strain, rebound to 95.33% of its original height, and exhibit hydrophobicity (water contact angle = 137.65°). In addition, the induction of MXene and the silane coupling agent endows the aerogel with enhanced electronegativity and charge density. These properties enable the CNF/MXene aerogel to harvest energy with an output voltage of 100 V and a short-circuit charge density of ∼900 nC cm^-3, while maintaining stability for 1000 cycles. This aerogel holds great application potential in the field of self-powered sensing and raindrop energy harvesting.